Rice production in China has more than tripled in the past five decades mainly due to increased grain yield rather than increased planting area. This increase has come from the development of high-yielding varieties and improved crop management practices such as nitrogen fertilization and irrigation. However, yield stagnation of rice has been observed in the past ten years in China. As its population rises, China will need to produce about 20% more rice by 2030 in order to meet its domestic needs if rice consumption per capita stays at the current level. This is not an easy task because several trends and problems in the Chinese rice production system constrain the sustainable increase in total rice production. Key trends include a decline in arable land, increasing water scarcity, global climate change, labor shortages, and increasing consumer demand for high-quality rice (which often comes from low-yielding varieties). The major problems confronting rice production in China are narrow genetic background, overuse of fertilizers and pesticides, breakdown of irrigation infrastructure, oversimplified crop management, and a weak extension system. Despite these challenges, good research strategies can drive increased rice production in China. These include the development of new rice varieties with high yield potential, improvement of resistances to major diseases and insects, and to major abiotic stresses such as drought and heat, and the establishment of integrated crop management. We believe that a sustainable increase in rice production is achievable in China with the development of new technology through rice research.
The objective of this study was to elucidate the roles of sugar in the formation of root systems. Several parts of the seminal root were investigated to determine their sucrose, glucose and fructose contents, and the activity and the in situ localization of the activities of two kinds of metabolic enzymes, invertase and sucrose synthase, which hydrolyze sucrose. The sucrose, glucose and fructose concentrations in the 0-1 cm section from the root apex were three to five times those in the other sections. The invertase and sucrose synthase activities were also higher in the apical section. The in situ localization of invertase activity was detected in the cell elongation zone of the seminal root using histochemical method. The sucrose synthase activity was detected in the cell elongation zone of the seminal root and the root apices of lateral roots. These results suggested that sucrose is transported to the root elongation zone and the surrounding tissue of the lateral root primordia, and is cleaved into glucose, fructose, and UDP-glucose by invertase or sucrose synthase. This suggested that sucrose contributes to root formation by serving as the energy source, the carbon source for cell wall synthesis, and as a compatible solute for cell elongation.
Previously, we demonstrated that root tips in drying soil communicate with shoots for stomatal closure in rainfed lowland rice, despite further water being available at depth. This study examines variation between two lines in root signals. Rice lines CT9993 and IR62266 were grown in the field, and in the greenhouse with the split-root root-sever wax-layer system, to investigate their responses to mild and severe water deficit by monitoring stomatal conductance (gs), leaf water potential and leaf ABA concentration. In the greenhouse, root systems were divided, withholding water from one portion, and in some cases, severing the droughted portion of roots to remove the signal. Wax layers differing in strength were placed at hardpan depth. Roots of CT9993 were better able to penetrate the wax layers. IR62266 exhibited stronger responses than CT9993, with IR62266’s stomatal conductance dropping sharply under water deficit, and recovering at slower rates but less completely, when roots subjected to drying soil were severed. The greater stomatal response in IR62266 was associated with a higher leaf ABA concentration during early water deficit, which in turn was associated with its greater number of roots in drying soil. In the field, a second reduction in gs was observed under severe water deficit, with stronger signals in IR62266 associated with more conservative water use as soil drying intensified. To better exploit subsoil water in mild or transient water deficit, selection for reduced root signals might be warranted.
The effects of relative light intensity (RLI) on the growth, yield and curcumin content of turmeric (Curcuma longa L.) were examined in Okinawa, Japan. The plants were shaded with white nets with different mesh sizes for maintaining respective RLI. Five RLI, 100 (without shading), 82, 79, 73 and 59% in 2004-2005 and four RLI, 100, 68, 52 and 48% in 2005-2006 were evaluated. In the first experiment, plant height increased markedly, but the number of leaves and tillers, and SPAD value increased slightly in the plants grown at 59-82% RLI compared with control (without shading). Turmeric shoot biomass and yield increased significantly at 59-82% RLI and they were highest at 73% RLI in the first experiment. Curcumin content of turmeric increased markedly at 59-73% RLI as compared with the control in the first experiment. Similar results in plant growth, shoot biomass, yield and curcumin content were obtained in the second experiment, but the effects of RLIs were smaller than in the first experiment because of late planting. This study indicates that turmeric is a partial shade-tolerant plant that could be cultivated at around 59-73% RLI for higher yield and curcumin content in Okinawa. However, the degree of RLI required for better turmeric cultivation may vary with the place, year and irradiance level.
We measured the concentration of polyols (pinitol, ononitol, and myo-inositol), which are known to have health-promoting and/or disease-preventing functions, in the common ice plant (Mesembryanthemum crystallinum L.) cultured under salt- and drought-stressed treatments. In NaCl-treated plant the concentration of pinitol/ononitol increased with increasing NaCl concentration in culture solution. The maximal concentration was 3.6 mg g-1 FW, which was found in the shoot top, followed by small side shoots (2.1 mg g-1 FW) of mature plants grown with 400 mM NaCl for 35 ds. The drought stress also accelerated the accumulation of pinitol/ononitol. The maximal concentration was 1.2 mg g-1 FW, which was found in the shoot top of plants under the stress for 25 ds. The myo-inositol increased in salt-stressed plants at 3 ds after the start of the treatment and then decreased with the lapse of time during stress. The concentration of polyols in the ice plant was comparable to that in the other species reported to accumulate polyols at high levels. Radical scavenging activity evaluated by DPPH assay was increased two-fold by 400 mM NaCl treatment, which was twice as high as that in the leaves of lettuce (Lactuca sativa L.). These results indicated the high potential of the ice plant as a polyol-rich high-functional food.
The allelopathic potential of 102 Bangladesh rice cultivars (60 traditional and 42 high yielding) against four test plant species, cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), barnyardgrass (Echinochloa crus-galli (L.) Beauv) and Echinochloa colonum (L.) Link was determined for shoot and root growth. In the two-way analysis of variance, the effect of rice cultivar, test plant species and their interactions were significant (P<0.0001). The significant effects of cultivar and the interactions indicated that there was variation in allelopathic activity among the rice cultivars. This result suggests that rice cultivars which were allelopathic against one plant species were not always allelopathic towards other plant species. However, the high-yielding rice cultivar, BR17 marked the greatest inhibitory activity with an average of 59% growth inhibition on shoots and roots of cress, lettuce, barnyardgrass and E. colonum. The present research suggests that BR17 is the most allelopathic among 102 Bangladesh rice cultivars and may be one of the candidates for research on Bangladesh rice allelopathy for isolation and identification of allelochemicals.
The objective of this study was to establish the correlation of the chlorophyll meter (SPAD) readings with the contents of chlorophyll (Chl) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), the gross photosynthetic rate (PG), and the maximum quantum yield of photosystem II (PSII) (Fv/Fm) in flag leaves of rice (Oryza sativa L.) in ripening stage. The SPAD readings significantly correlated with the Chl content, the Rubisco content, PG and Fv/Fm (R2=0.848, 0.648, 0.671 and 0.712, respectively), which suggests that the SPAD meter has the potential to estimate the photosynthetic capacity of the flag leaves. However, both PG and Fv/Fm had a stronger relationship with the Rubisco content than the SPAD readings, indicating that the PSII photochemical and CO2 assimilation capacities are strongly influenced by the Rubisco content. Therefore, accurate calibration would be indispensable to obtain the physiological information from the SPAD readings of flag leaves.
The response spectrum for green light induced-acceleration of heading in wheat cv. Norin 61 was investigated using narrow-bandwidth (10 nm) green light within the range of 520-550 nm. Heading was observed from approximately 30 days after emergence. The earliest heading was observed at 540 nm, which suggests the presence of a green light photoreceptor different from hitherto known photoreceptors.
It is important to measure the individual leaf area and leaf area index (LAI) of sago palm (Metroxylon sagu Rottb.) to determine the appropriate planting density and maintain populations that are highly productive with regard to starch production. However, the accurate estimation of sago leaf area from the entire leaf profile or the projecting area of the plant is not possible. Thus, we developed a method for estimating leaf area of sago palm after trunk formation by integrating the leaflet areas. All leaflets were diagrammatically converted to rectangles, each having the same area as that of the corresponding leaflet, and these rectangles were arranged on the rachis to initiate the shape of a leaf without overlapping leaflets and gaps between their bases and between their tips. The leaf shape thus produced by the arrangement of these rectangles was represented as ellipsoidal in the apical half and as trapezoidal in the basal half. The ratios of the estimated to the actually measured area of the apical and the basal half of the leaf were 99-107% and 94-108%, respectively. The ratio of the estimated area of the whole leaf to the measured area was 98-104%. From these results, the method for estimating the whole leaf area by converting the leaflets diagrammatically to rectangles, and calculating the area as the sum of the ellipsoidal apical half and trapezoidal basal half, is considered to be accurate and simple.
In this study, we collected native aromatic rice cultivars from north, east and northeast of Afghanistan, and check cultivars from Japan, Thailand and India. We characterized some important agronomic characters such as plant height, panicle number per plant, grain number per panicle, 1,000-grain weight, grain length and grain width to find the desirable characters for breeding programs. Many of them were classified into tall culm rice according to IRRI index, but had thin and slender grain, and strong aroma which are favorable characteristics in Afghanistan and surrounding regions. The aromatic character was characterized by three methods, 1.7% KOH sensory test, gas chromatography-mass spectrometry-selected ion monitoring (GC-MS-SIM), and polymerase chain reaction (PCR) analysis. These three methods gave similar results. Six out of 10 Afghan native rice cultivars were aromatic and four non-aromatic. Among the check cultivars, Basmati 370, Jasmine 85, Izayoi, Oitakoutou and Jakouine were aromatic and Nipponbare non-aromatic. Improvement of aromatic and high yielding rice and reduction of plant height are the important objectives for rice breeding in Afghanistan. The results showed that Pashadi Konar from Afghanistan has the intermediate plant height, heavier 1,000-grain weight (32 g), longer grain (11 mm) and favorable aroma. Therefore, this cultivar may be a good source of aromatic rice germplasm in Afghanistan. To clarify the genetic nature of aroma in rice, we crossed non-aromatic cultivar Nipponbare with aromatic cultivar Jasmine 85, and examined the aromatic character in the F2 generation by 1.7% KOH sensory test and PCR analysis. Non-aromatic and aromatic characters were segregated at a ratio of 3:1, showing that aroma is controlled by a single recessive gene.
We are maintaining five Moricandia arvensis monosomic addition lines of Raphanus sativus carrying R. sativus cytoplasm (autoplasmic MALs) and twelve M. arvensis MALs of R. sativus carrying M. arvensis cytoplasm (alloplasmic MALs) from BC6 to BC8 generation, and newly produced five M. arvensis disomic addition lines of R. sativus (autoplasmic DALs) and seven M. arvensis DALs of R. sativus carrying M. arvensis cytoplasm (alloplasmic DALs) from selfing and sib-crossing of the MALs and DALs in S3BC5 and S2BC6 generations. The structural, biochemical and physiological characteristics related to photorespiration of these MALs and DALs were compared to study the genetic mechanisms of the C3-C4 intermediate photosynthesis in the individual chromosomes of M. arvensis. The CO2 compensation point of the autoplasmic and alloplasmic DALs (RMa-b and MaR-b DALs) with one pair of M. arvensis ‘b’ chromosome were 29.4 and 30.1 μmol mol-1, respectively, which were significantly lower than that of other DALs and MALs as well as R. sativus (34.5 μmol mol-1). An immunogold electron microscopic study of the P-protein of glycine decarboxylase (GDC) in photosynthetic cells of the RMa-b DAL revealed that the bundle sheath cell (BSC) mitochondria were more intensively labeled for the protein than the mesophyll cell (MC) mitochondria. The ratio of the labeling density of the BSC mitochondria to that of the MC mitochondria was 1.13, which lies between values in M. arvensis (2.66) and R. sativus (0.76). These data suggest that the ‘b’ chromosome of M. arvensis genome controls the expression of C3-C4 intermediate characteristics.
Pedigree analysis was conducted for early maturing wheat cultivars developed in Japan. Materials used for this analysis were mainly developed at Nagano Agricultural Experiment Station (Tozan lines). In a recently released Tozan line, the maximum number of generations traced in the pedigree, total number of ancestors in the pedigree and total number of ancestors except common ones was 11, 222 and 94, respectively. Chunaga contributed 24.0% of the genetic background of Tozan lines. Seven ancestors, collectively, contributed 51.5% to the gene pool. Hiyokukomugi had the highest mean coefficient of parentage to Tozan lines and the mean value was 0.216, followed by Kinuiroha (0.213), Norin 61 (0.206), Mikunikomugi (0.205) and Tokai 80 (0.194). The mean coefficient of parentage between Tozan lines and cultivars in the Kanto-Tokai region, Kinki-Chugoku-Shikoku region and Kyushu region was 0.165, 0.155 and 0.157, respectively. Tozan lines more related to cultivars in the Tohoku region tended to be late heading and more cold-tolerant. Tozan lines more related to Ayahikari or Kinuazuma tended to be early maturing. Fukuhokomugi, which was a high yield cultivar and often used as a cross parent, did not contribute to high flour protein. KS831957 showed a positive effect on the crude protein content of flour. In general, Tozan lines had no specific cultivars used extensively as a cross parent having significant influence on yield or flour quality.
Ramie (Boehmeria nivea L.Gaud) is planted as an important fiber crop in China. Randomly amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers were used for the first time for the detection of genetic polymorphism of 37 ramie accessions (29 wild genotypes and 8 commercial varieties) collected from various geographical regions of West China. The objectives of this study were: 1) to examine the genetic diversity of four species in genus Boehmeria Jacq.: B. clidemioides var. diffusa, B. nivea L. Gaud, B. longispica Steud, and B. macrophylla Hornem; and 2) to determine the genetic distance of the four species by these methods. Laportea cuspidata (Wedd.) Friis was used as an outgroup species. The results showed that 375 (17 monomorphic fragments) strips were amplified by 31 RAPD primers, while 266 (10 monomorphic fragments) strips by 18 ISSR primers. On the average, each RAPD and ISSR primer amplified 12.1 and 14.8 strips, respectively. Based on the appearance of the markers, the genetic relationships were analyzed using unweighted pair-group method of arithmetic average cluster analysis (UPGMA) and the genetic Dice coefficients were calculated. Clustering analysis indicated that the 37 accessions were classified into four clusters which belong to 3 sections (including Section Phyllostachys, Section Tilocnide and Section Duretia). The overall grouping pattern of clustering corresponded well with traditional botanical taxonomy. Principal component analysis (PCA) confirmed the patterns of genetic diversity observed among the species. These results suggested that RAPD and ISSR were efficient approaches suitable for taxonomic analysis of ramie wild materials. The results provided valid guidelines for collection, conservation, and characterization of Boehmeria genetic resources.
An alternative method to classify amylose content in rice was developed. In this method, based on amylose-iodine colorimetry, a standard color chart was used instead of a spectrophotometer to successfully classify a wide range of cultivars with known and unknown amylose content. This is a rapid low-cost method that may be useful for prediction of amylose content in rice for breeding purposes.
Excessive nitrogen fertilization results in low nitrogen-use efficiency. To improve nitrogen management for high yield and high nitrogen efficiency in rice and wheat, we developed a knowledge-based nitrogen fertilization model by integrating the quantitative relationship between N fertilization and yield target with respect to N supply and demand balance. The total amount of nitrogen and ratio of basal to top dressing nitrogen could be determined by this nitrogen fertilization model, and the desirable nitrogen fertilizer strategies could be made under the conditions of different climates, soil types and managements. Furthermore, the function of dynamic regulation of pre-designed N dressing rate could be determined by using the nitrogen fertilization model on the basis of actual growth status under a specific production system. The nitrogen fertilization model is evaluated using the data from field experiments of rice and wheat at Nanjing, and the results on crop growth pattern and N use showed that the grain yield and N recovery were markedly improved by the N fertilization plan given by the model. The nitrogen fertilization model can be used as guidance for quantifying N fertilization strategy in cereal crop production.
We examined the effects of seeding rate, 50 or 150 seeds m-2, nitrogen (N) application rate at active tillering and jointing, 4 and 2 g N m-2, respectively, or none, and N application rate at anthesis, 0, 2, 4, or 6 g N m-2, on grain yield and protein content of a bread wheat cultivar, ‘Minaminokaori’, during the 2004-2005 crop season in southwestern Japan. Grain yield was similar at a seeding rate of 50 and 150 seeds m-2. It was higher when 4 and 2 g N m-2 were applied at active tillering and jointing, respectively (4-2N), than when no N was applied at these stages (0-0N). However, it was not influenced by N application rate at anthesis. Grain protein content was similar at 50 and 150 seeds m-2. It was higher in 4-2N than in 0-0N. It was the highest when 6 g N m-2 was applied at anthesis, followed by 4, 2, and 0 g N m-2. The SPAD value at anthesis was higher at 50 than 150 seeds m-2, but leaf area index (LAI) at anthesis was similar at 50 and 150 seeds m-2 and protein content of grain was nearly the same at 50 and 150 seeds m-2 irrespective of N application rate at anthesis. LAI and the SPAD value were higher in 4-2N than in 0-0N and the protein content of grain was also higher in 4-2N than in 0-0N irrespective of N application rate at anthesis. Therefore, both LAI and the SPAD value may be important traits related to the N application rate at anthesis suitable for yielding wheat grain with a high protein content.
The Tibetan Plateau is one of the highest cultivated regions in the world. The objective of the present study was to compare wheat growth and grain yield in the high altitude region with those in a low altitude region. Two spring wheat cultivars were grown for two years at an experimental field in Lhasa (29°N, 3688 m above sea level) in the Tibetan Plateau in 2001 and 2003, and in Sapporo (43°N, 15 m above sea level), Japan in 2002 and 2003. In Lhasa, temperature throughout the growth period was lower and photoperiod before heading was shorter than in Sapporo. There was no significant difference in grain yield between Lhasa and Sapporo. Dry matter production was higher in Lhasa than in Sapporo. The crop growth rate before heading was similar in both locations, but the time to heading was 15 days longer in Lhasa than in Sapporo. Leaf senescence was more decelerated in Lhasa than in Sapporo. These results suggested that high dry matter production in Lhasa was mainly due to the longer growth period.
We examined the effects of cutting height and trampling over stubbles of the first crop on dry matter yield in twice harvesting of forage rice Oryza sativa L., Tachiaoba and Taporuri. Dry matter yield of the second crop, after the first harvest at the full-heading stage, increased with increasing cutting height. However, the dry matter yield of the first crop decreased with increasing cutting height. Overall, total dry matter yield did not vary with the cutting height. Dry matter yield and its components of the second crop were not greatly affected by the trampling treatment. At cutting heights of 15 and 5 cm from the base, the number of tillers developed from unelongated nodes was increased by the trampling treatment. Thus, although the number of tillers developed from the elongated nodes was decreased after the trampling treatment, the decrease is compensated for by the increased number of tillers from unelongated nodes.